The present invention relates to a conveying apparatus suitable for driving a number of carriers in such a manner that the front end of each carrier thrusts the rear end of the preceding carrier.
In prior art thrust-drive conveying apparatuses, the front end of a carrier thrusts the rear end of the preceding carrier along a traveling path, which includes linear and U-turn path sections. Travel in the linear path sections occurs without thrust problems. In the U-turn path sections, adjacent carriers are not aligned linearly, but angled to each other. The direction of the thrust acting on each of the mutually angled carriers differs from the direction in which the preceding carrier moves. The difference between the directions causes a great loss of thrust. Accordingly, in order to thrust the carriers smoothly and securely in the U-turn path sections, it is necessary to maximize the radius of curvature of these sections and drive the carriers with great thrust. One type of prior art conveying apparatus includes carriers formed with driven frictional surfaces for compressive contact with driving rotors, which frictionally drive the carriers. It is difficult to thrust these carriers in the U-turn path sections of a traveling path. Accordingly, in the U-turn path sections, these carriers are driven by an end-to-end traction system.
Thus, in the prior art conventional conveying apparatus, the carriers are driven by the combination of the thrust drive system and the end-to-end traction system. In the linear path sections, the rear ends of the carriers are thrusted. In each U-turn path section, the carriers are connected end-to-end, and a driving means applies thrust to one of them, which pulls the following carriers. Each carrier of the prior art apparatus needs to include connecting means for connection to and disconnection from others carriers. The traveling path of this apparatus needs to include means for automatically disengaging the connecting means. Thus the entire apparatus is complex in structure, expensive, and complex to control.
The object of the present invention is to provide a conveying apparatus that can solve the foregoing problems. A conveying apparatus according to the present invention comprises a guide rail and carriers. The rail includes a U-turn path section. Each carrier includes a load bar assembly including at least three load bars connected end-to-end by vertical pivot shafts in such a manner that the bars can pivot horizontally relative to each other. Each carrier also includes a load support supported by the associated middle load bar. Each carrier further includes a pair of front and rear trolleys supporting at least the front and rear end load bars, respectively. The trolleys are supported movably on and guided by the guide rail. The front and rear trolleys are fixed to and in parallel with the front and rear end load bars, respectively. The free ends of the front and rear end load bars protrude from the front end of the front trolley and the rear end of the rear trolley, respectively, so that the free end of the front end load bar of each carrier and the free end of the rear end load bar of the preceding carrier can contact together in the U-turn path section.
While each carrier is traveling in the U-turn path section, the free ends of the end load bars of its load bar assembly deviate only slightly from the center line of the path section (the locus of the center of width of each trolley). This makes it possible to position the free ends on the center line.
Accordingly, in the U-turn path section, the free end of the front end load bar of each carrier and the free end of the rear end load bar of the preceding carrier can contact together at a point (the thrust point between adjacent carriers) near and even very near to the center line of the path section. Depending on the shape of the free ends, they can contact together on the center line. As a result, the thrust of each carrier acts on the preceding carrier efficiently through the free ends of their end load bars in the U-turn path section. This makes it possible to thrust the carriers smoothly and securely in the U-turn path section.
The present invention removes the need to particularly enlarge the radius of curvature of the U-turn path section and/or provide an exclusive driving means for this section. It is consequently possible to promote the practical use of a conveying apparatus in which the front end of each carrier thrusts the rear end of the preceding carrier.
In another embodiment, each of the carriers may include a load bar assembly including at least five load bars connected end-to-end by vertical pivot shafts in such a manner that the bars can pivot horizontally relative to each other. Each of the carriers may also include a load support supported by the associated middle load bar. Each of the carriers may further include a pair of front and rear load trolleys supporting the front and rear ends respectively of the associated middle load bar in such a manner that these trolleys can rotate relative to the bar each on a vertical pivot shaft. Each of the carriers may further include a pair of front and rear guide trolleys supporting the front and rear end load bars respectively.
Thus, the present invention makes it possible to drive long carriers smoothly in the U-turn path section even if this section has a relatively small radius of curvature. Further, the present invention prevents excessive torsional stress from acting on the middle load bars of the carriers due to loads.
The free ends of the end load bars may be convexly arcuate in plan view. In the U-turn path section, the convexly arcuate ends of the end load bars of adjacent carriers can contact together on or closely near the center line of this section. This makes it possible to thrust the carriers effectively in the U-turn path section.
The junction between each end load bar and the trolley supporting the end load bar may be near the joint between the end load bar and the adjacent load bar.
The present invention minimizes the overall length of each end load bar. Additionally, the present invention reduces the deviation of the joint between each end load bar and the adjacent intermediate load bar from the U-turn path section. This makes it possible to thrust the carriers more smoothly and securely in the U-turn path section.
The load bars of each load bar assembly may be connected together in such a manner that the mutually connected ends of adjacent load bars are positioned on or over each other. At least one side of each load bar may form a driven frictional surface continuing flush and linearly to the driven frictional surfaces of the other load bars in a linear path section of the guide rail.
Additionally, the present invention enables continuous friction drive of the carriers by means of their load bar assemblies in the linear path section.